It would appear that Fx 42 has broken the ability for FEBE to restore extensions. I am working on a fix. In the meantime, you can still restore extensions by using Tools > Add-ons > (gear icon) > Install Add-on From File...

For the time being, themes can still be restored with FEBE > Restore > Restore Themes., but this may break also.

What specific problems are you encountering? Are you getting any FEBE related messages in the error console (CTRL-SHIFT-J, type febe in the 'Filter output' field in the upper right of the console window, copy/paste in your response)?

I don't have a Tail CD, nor the Tor Browser installed, so I cannot test it myself.

What type of backup are you trying to perform (Full profile, selective, both)? It appears that FEBE is failing while trying to "phone home" to Mozilla when getting your installed add-ons information. Try running FEBE Options > Advanced > Attempt to load and save extension data to see if it can complete without errors.

There is also a reference to 'getFirstPartyURI' failing. This is a Tor specific error. You say your Tor browser is based on Fx 38.5.0. Try installing FEBE v8.6 or v8.7 and see if it makes a difference.

cbaker_admin wrote: It appears that FEBE is failing while trying to "phone home" to Mozilla when getting your installed add-ons information. Try running FEBE Options > Advanced > Attempt to load and save extension data to see if it can complete without errors.

There is also a reference to 'getFirstPartyURI' failing. This is a Tor specific error. You say your Tor browser is based on Fx 38.5.0. Try installing FEBE v8.6 or v8.7 and see if it makes a difference.

Any idea on a Debian Linux system where that data would be saved to see if it has worked?

Found it - with Tails you cannot save to any another location than Home > Tor Browser.

Febe created directories(FEBE 2015 27.12 00.23.34 & FEBE 2015 27.12 00.41.53 - tried it twice) according to the set back up directory settings ( /home/amnesia/Tor Browser/febe) but they are both empty,

Interesting. If files can only be written to Home > Tor Browser perhaps you can create a new Fx profile in that location.

Start Fx from the command line with [path_to_Firefox_executable]/firefox.exe -p. This will open the profile manager dialog. Follow the prompts and create a new profile in some sub-directory of Tor Browser.

Install FEBE into the new profile and set the backup destination directory in some other sub-directory of Tor Browser.

If the FEBE Options > Advanced > Attempt to load and save extension data is successfull, the data should be in a file named 'febeExtensionData.json' in your new profile folder.